For times when Windows CE or Windows Mobile is just too processor intensive, takes too much power, or needs to much memory, you use the .NET Micro Framework, formerly known as SPOT (Smart Personal Objects Technology). The .NET Micro Framework is in verion 2.5 with 3.0 on the way. It is for applications such as Sensor Nodes, Aux displays, Health Monitoring, Remote Controls, and Robotics.
The .NET Micro Framework provides you with the tools necessary to develop your firmware as managed C# applications. You get a specialized version of the common runtime language (CLR) and the .NET Framework. And you use Visual Studio as your development environment.
An article on developer.com entitled Explore the Microsoft .NET Micro Framework gives you the steps in getting started with .NET Mirco Framework. The article describes how to build your first Micro Framework project.
Download the software developer kit from Microsoft .NET Micro Framework SDK V2.5.